1. Field of the Invention
The invention relates to a device for cleaning an ink jet print head, particularly in a postage meter and/or addressing machine.
Prior art postage meter and/or addressing machines on the market print primarily with ink rollers or thermal print heads.
Recently effort has been directed to exploiting the advantages of ink jet printing to the field of applying postage and/or addressing mail by machine. The printing operation is thereby contact-less by means of ink jet print heads. Reference is had, in this context, to German Patent DE 44 24 771 C1 and to German Utility Model DE 94 20 734 U1.
A postage meter has been proposed in German Patent DE 196 05 014 C1 in which the letters are conveyed upright, tilting slightly backward, with the aid of a conveyor belt.
The letters there rest on a guide plate with a printing window in which the ink jet print head is fixed. The letter is moved past the printing window or ink jet print head and during this time is imprinted on the side facing away from the observer. The problem of ink jet print head cleaning and sealing, however, is not addressed there.
A device for cleaning an ink jet print head has become known from international publication WO 96/15908, wherein the ink jet print head is secured so as to be pivotable out of a printing position into a cleaning position and/or sealing position and vice versa. A cleaning and sealing device is also disposed behind the guide plate but in such a way that it is linearly adjustable toward and away from the ink jet print head.
The cleaning and sealing device includes a sealing cap, adapted to the ink jet print head, with suction slits for each row of nozzles. The device also includes a transversely adjustable wiper lip and a downstream suction pump.
In the sealing cap, on one end, a vacuuming region is also provided, with a central suction opening for the wiper lip. The wiper lip can be adjusted with a spindle drive. In that process the wiper lip slides under pressure along the nozzle face of the ink jet print head and in so doing carries away residual ink located thereon. In the associated vacuuming region, the wiper lip is stopped and vacuumed off. Via the suction opening, however, only the residual ink located in the lower middle part of the wiper lip is vacuumed off, so that the next time the nozzle face is wiped off there is a danger that it will smear. A further consideration is that when the wiper lip is separated from the nozzle face, some of the residual ink remains behind on the print head edge because of adhesion; it can collect into a droplet and then drip into the space located below the ink jet print head. There is also the danger that when the cleaning and sealing device is disconnected from the ink jet print head, the wiper lip, which is curved under pressure, will suddenly snap back and throw off some of the residual ink still present on the wiper lip by centrifugal force. Not only can it thus cause undesired contamination but it can even cause damage in the device, especially if the ink is conductive.
A further ink jet printer is known from Japanese patent disclosure JP 08 048043, in which a compartment with a replaceable, absorbent filling for cleaning the wiper lip is provided in the housing of an ink jet print head.
It is a desirable goal to improve cleaning the ink jet print head and maintaining the ink jet print head clean.